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Math Help - circle

  1. #1
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    circle

    Hey, i got my final GCSE maths test (non calc) which starts in around 1 and a half hours!
    I don't get this question:

    EDIT: HERE IS THE GRAPH. SORRY IN A RUSH AND FORGOT LOL.



    A, B, C and D are points on the circumference of a circle, centre P.
    AC is the diameter of the circle.

    Angle DAC = 20

    (a) Find the size of angle ACD

    (b) Find the size of angle DBC
    Give a reason for your answer
    Last edited by Danielisew; June 4th 2007 at 03:44 AM.
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  2. #2
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    please help!

    I need some help real quick!

    Need to leave in 40 mins!
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  3. #3
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    Angle ADC=90 because a circumferential angle leaning on the diameter is a right angle (sorry for my english, I don't know if I have used the correct expressions)

    so Angle ACD = 180 - 20 - 90 = 70
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  4. #4
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    sorry, I guess it's called "inscribed angle" not "circumferential angle"...
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  5. #5
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    so, every inscribed angle that subtends a diameter is a right angle..
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  6. #6
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    Thanks!

    What about part (b) to the question?

    SORRY THERE IS MEANT TO BE A LINE FROM B - C

    I was in such a rush i missed it out..

    Please do part (b)!

    Thanks!!
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  7. #7
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    please someone do part B!

    I need to leave in 10 mins!
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  8. #8
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    I think angle DBC is also 20 because both subtend the same arc.
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  9. #9
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    GOOD LUCK m8
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  10. #10
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    oh yeah!

    Ok thanks!!

    THANK YOU VERY MUCH WISH ME LUCK
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